Gases Part 1

Gases Part 1

By Abby Fancsali

Characteristics of Gases

• Gases have unique Properties because of the space between the molecules

• Gases are considered Fluids

• Gases expand​ over an area and can be compressed into smaller spaces

• Gases Diffuse from one area to another and will mix together​

Section 1.1: Gases and Pressure

• Pressure: The force of something on a given surface area

  • P= F/A

    • A smaller area can give result in more pressure

  • Unit is Newtons (N)​

  • Caused by the force molecules exert on a surface

    • In Gases this involves the collisions of molecules over a surface

Section 1: Gases and Pressure

• Practice Problem:

​A force of 150 N is being applied over an area measuring 0.50 m². Calculate the pressure on the object.

• Equation: P=F/A

  • Force=150 N

  • Area= 0.50​

Section 1.2: Measuring Pressure

• Barometer: A tool for measuring atmospheric pressure

• Manometer​: A tool for Measuring pressure of an enclosed sample

​Manometer​:

Section 1.3: Units of Pressure

• We use different units for measuring gas pressure depending on what we are looking at

  • Pressure unit 1: millimeters of Mercury (mm Hg)

    • Also called the torr

    • used to measure atmospheric pressure

  • Pressure Unit 2: Atmosphere (atm)

    • 1 atmosphere = 760 atm Hg

    • Used to compare a sample to atmospheric pressure

  • Pressure Unit 3: Pascal (Pa)

    • Force of one Newton over one square unit

    • Kilopascals are used because one pascal can be very big

Section 1.3: Units of Pressure

​STP: Standard Temperature and Pressure conditions, 1 atm and 0° C

Section 1.4: Solving Problems with Pressure

• Example 1: The Average atmospheric Pressure in Denver Colorado is 0.830 atm. Express this pressure in the following units

  • mm Hg

  • k Pa

• Step 1: Identify the relationship between the units we want and the unit we have

  • 1 atm =760 mm Hg

  • 1 atm = 101.325 kPa​

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Section 1.4: Solving Problems with Pressure

• Example 1: The Average atmospheric Pressure in Denver Colorado is 0.830 atm. Express this pressure in the following units:

  • mm Hg

  • k Pa

• Step 2: Plug in our relationships into conversions

  ​​

Section 1.4: Solving Problems with Pressure

• Example 2: A weather report gives a current atmospheric pressure reading of 745.8 mm Hg. Express this reading in kilopascals

• Step 1: Identify the relationship between the units we want and the unit we have

  • We don't have a direct conversion from mm Hg to KPa, but what unit can we use to make the switch?

  ​​

Multiple Choice

Which Unit can we use to go between mm Hg and kPa

• Torr

• Atmosphere

• pounds per square inch

• Pascales

Section 1.4: Solving Problems with Pressure

• Example 2: A weather report gives a current atmospheric pressure reading of 745.8 mm Hg. Express this reading in kilopascals

Section 1.5: Dalton's law of Partial Pressure

• When you have a mixture of gases, each individual gas exerts its own pressure separated from all the other gases pressure

  • Partial Pressure: The pressure of ​each gas in a mixture

• Dalton's law of Partial Pressures: the total pressure of a gas mixture is equal to the sum of the individual pressures of each gas in the mixture

  • P_T= P₁ + P₂ + P_3........​

Section 1.5: Dalton's law of Partial Pressure

Partial Pressure Sample Problem: Blast furnaces give off many unpleasant and unhealthy gases. If the total air pressure is 0.99 atm, the partial pressure of carbon dioxide is 0.05 atm, and the partial pressure of hydrogen sulfide is 0.02 atm, what is the partial pressure of the remaining air?

• Step 1: Identify what we have

  • P_T = 0.99

  • P₁=0.05

  • P₂=0.02​

• Step 2: Plug those values into the equation